Typically, in an engine, a crankshaft includes counterweights, where each counterweight is attached to each of the crankshaft's cheeks, in order to balance the engine. However, this kind of counterweight arrangement is difficult to manufacture and expensive too.
U.S. Patent Publication 2012/0048226 relates to a crankshaft for an engine having an odd number of cylinders. The crankshaft includes a central pin coupling a first and a second asymmetric counterweight and a pair of pins coupling cheeks absent counterweights.